There are several types of apparatus that can be employed for industrial and structural uses in order to absorb energy, such as from a transmitted load. For example, high cycle blow molding apparatus employ mold or die halves which can “bounce” as a consequence of opening and closing the dies, i.e., principally the impact of closing the dies. Such bounce can produce defects in the molded product resulting in increased scrap, additional maintenance and increased downtime of the blow molding apparatus. Consequently, the throughput/efficiency of the blow molding apparatus is adversely impacted. To alleviate difficulties associated with the foregoing, conventional shock absorbers have been employed to convert the impact energy of the bounce as dissipated heat.
More specifically, these shock absorbers typically include at least one piston assembly, which is disposed within an enclosed cavity or housing, and coupled to the machine under load. In operation, a transmitted shock or impact load creates: (i) movement of the piston assembly, (ii) a change in pressure of a contained incompressible hydraulic fluid in the cavity, and (iii) flow through at least one orifice that results in conversion of the applied kinetic energy to heat. The force of the transmitted shock or impact load is reduced by the shock absorber, thereby lowering the transmitted load from other parts of the machine or other attached structure.
For proper operation, shock absorbers as described above require at least one dynamic seal interposed between the moving parts to prevent fluid leakage, and/or the ingestion of air into the hydraulic cavity of the housing. Inasmuch as blow molding or other apparatus routinely undergo a high number of cycles, it is common for the dynamic seals to fail prematurely, requiring costly repair and maintenance. Additionally, the replacement of either the hydraulic seals, or the entire shock absorber assembly, can adversely impact manufacturing schedules or other time-critical events for the purpose of repairing and/or replacing the affected assemblies. It will be appreciated that avoiding down-time for such high throughput machines is an ongoing and important goal.
It is, therefore, desirable to provide an effective and reliable shock absorbing apparatus which mitigates the need for dynamic seals and the failure modes associated therewith. Furthermore, it will be appreciated that there is a competing and prevalent need to reduce complexity, improve reliability, and lower associated costs of such high cycle, dynamic shock absorbing apparatus.